Popular Social Bookmarking Websites:

Social bookmarking is an online service which enables the users to add, annotate, edit, and share bookmarks of web pages they like. Social bookmarking websites suitable for SEO link building These sites give one way quality backlinks. At the same time popular sites like digg, sumbleUpon can give you tons of traffic quickly.

1) http://blogMarks.net/
2) http://fark.com/
5) http://delicious.com/ Delicious, founded in 2003, popularized the terms "social bookmarking" and "tagging".
6) http://digg.com/ Very pouolar. You web server may crush with tons of trafic if you can reach digg front page.
9) bookmarks.yahoo.com
10) http://reddit.com/
12) BlogsVine.com - blog sharing
14) http://dropjack.com/ A digg like voting based bookmarking website.
18) diigo.com
19) www.boxedup.com free wishlisting site. Bookmarking for the online shoppers.
20) www.linkagogo.com
21) www.netvouz.com - Surf smarter with your netvouz online bookmarks.
22) www.newsvine.com - news sharing site
27) www.StumbleUpon.com Another very popular bookmarkeing site.

Importance of Social Bookmarking in SEO:
Social Bookmarking is undoubtedly one of the prime techniques for off-site SEO. This helps to get higher ranks in search engine results for relevant targeted keywords. Although doing too many bookmarks within short period of time using only a few titles, keywords and very short descriptions may pose the risk of getting penalty for link spamming, this is still a good SEO option when done carefully and responsiblly.